i wouldnt buy any ocz drive if you want reliability, you want that get a samsung, intel or crucial. reliability is way more important than a little extra speed. ssd's are already quick
Honestly, I agree with this. I have a samsung ssd 830 256gb and it hasn't given me a single problem. Intel would be the other rock solid option I would go for. Crucial is also very reliable, just a touch less than the other two, but the m4 is an awesome ssd regardless. If you are set on either the 512gb agility or vertex, then I would go with the vertex.
Also there's 2 512gb vertex 4's listen on newegg and one of them is 5 stars after 7 reviews, the other 3 stars after 17 reviews. The former seems to be slower in 4k random write speed, but under its "notes", it still shows max IOPS is also 120k. Oh, and its a lot cheaper ($399.99 former as of this writing vs $464.99 latter and $359.99 agility after rebate). Also, the former vertex 4 has a slightly higher item# in NewEgg which leads me to believe its the newer model.